The invention is directed to a method for grinding a rail head surface which consists of a running surface, a rounding off of the head and outer surfaces, the so-called running and guide surfaces of rails or the like, where the running and/or guide surfaces are ground by an endless revolving abrasive belt movable against the surfaces, as well as an apparatus for performing this method.
The machining of the running and guide surfaces of rails, and this applies to wide bottom flange rails as well as to streetcar rails, assumes a constantly increasing significance within the framework of rail improvement and conservation.
Welding beads as formed, for example, by thermite welding, excess welding deposit, which occurs in electric build-up or resurfacing welding of new rails as well as rail sections to be repaired, however also undulations or rail corrugations causing unevenness in the running or guide surfaces of rails used for railroad tracks, which impair the rolling properties of rail-borne vehicles to a large extent, are removed by the grinding process.
A mobile rail grinding machine for performing such a grinding process is known from DE-OS 28 01 110, where the running surface is machined, in accordance with the embodiment in FIG. 6 of that reference, by an endless abrasive revolving grinding belt, which is pressed against the running surface of the rail. Herein the grinding belt is supported on the one hand by a drive roller and on the other hand by an additional roller serving for reversal arranged to be spaced from the driver roller. Both these rollers are rotatable around a horizontal axis which extends transversely to the longitudinal axis of the rail. This means that the abrasive belt revolves in the direction of the rail and thus in the travel direction or counter to the travel direction of the machine. The drive roller as well as the reversing roller are either entirely cylindrical or designed to be slightly arched outwardly or convex for better guidance of the abrasive belt. This entails that such a grinding process exclusively leaves an even surface on the running surface of the rails and removes unevenness or welding beads only in this region.
In order to completely machine, for instance, convex running surfaces, several such grinding units are arranged consecutively in the machine and each successive grinding unit is rotated with respect to the preceding grinding unit through several angular degrees in the longitudinal direction of the rail. After this method of machining, the running surfaces consist of several flat surfaces respectively inclined with respect to each other by several angular degrees, which approach very closely the desired shape of the running surface, however, without ever reaching same. The running surface will always have a polygonal cross-section. Furthermore, such a grinding method has the considerable disadvantage that the detached grinding dust moves or flies in the longitudinal direction of the rail and can cling to the rail or its running surface This previously known device entails considerable financial expense and is in spite of that unsuitable for machining welding beads at rail connections and for short pieces of rail which are repaired prior to installation by resurfacing by welding.
A device for grinding the running surface of rails is also known from EP-PS 0 110 246, which has a considerably simpler and therefore more economical construction. Here also the head or running surface is machined by means of an endless revolving abrasive belt, which is guided by a drive roller and a contact pressure roller which are both rotatable around a horizontal axis extending transversely to the rail. Thus, in this case also the abrasive belt revolves in the longitudinal direction of the rail, so that also in this case there always exists a polygonal head or running surface after the machining or grinding process. According to the embodiment in FIG. 4 of EP-PS 0110 246, the contact pressure roller is indeed designed as a profile roller, whose free cross-section corresponds to the running surface of a rail head. Such a profile contact pressure roller results, however, in an undesirable stretching in the edge regions of the abrasive belt, which entails a very rapid wear or a quick destruction of the abrasive belt. This is the reason why such a profile contact pressure roller is not used in actual practice.